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61.
Choudhary MI Nur-E-Alam M Akhtar F Ahmad S Baig I Ondögnii P Gombosurengyin P Atta-ur-Rahman 《Chemical & pharmaceutical bulletin》2001,49(10):1295-1298
Five new peltogynoids, irisoids A-E (1-5), have been isolated from the underground parts of Iris bungei. The structures of the new compounds were established on the basis of spectroscopic methods and were found to be 1,8,10-trihydroxy-9-methoxy-[1]benzopyrano-[3,2-c][2]-benzopyran-7(5H)-one (1), 1,8-dihydroxy-9,10-dimethoxy-[1]benzopyrano-[3,2-c][2]-benzopyran-7(5H)-one (2), 1,10-dihydroxy-8,9-dimethoxy-[1]benzopyrano-13,2-c][2]-benzopyran-7(5H)-one (3), 1,8-dihydroxy-9,10-methylenedioxy-[1]benzopyrano-[3,2-c][2]-benzopyran-7(5H)-one (4), and 1,8,11-trihydroxy-9,10-methylenedioxy-[1]benzopyrano-[3,2-c][2]-benzopyran-7(5H)-one (5). The structure of irisoid B (2) was established unambiguously by X-ray diffraction study. 相似文献
62.
D. Varshney R.N.P Choudhary C. Rinaldi R.S. Katiyar 《Applied Physics A: Materials Science & Processing》2007,89(3):793-798
The polycrystalline samples of Ba-modified Pb(Fe1/2Nb1/2)O3 (i.e., (Pb1-xBax)(Fe1/2Nb1/2)O3 PBFN, with x=0,0.05,0.07) were synthesized by a mechanosynthesis (i.e., high-energy ball milling) route followed by a mixed
oxide method. Structural analysis provides the information on formation of single-phase orthorhombic structure on substitution
of a small amount (x=0.07) of Ba at the Pb-site of Pb(Fe0.50Nb0.50)O3 (PFN). The ferroelectric–paraelectric phase transition in PFN was observed at 383 K, which decreases on increasing Ba-concentration
in PBFN. Detailed studies of dielectric properties of PBFW show the following: (i) diffuse phase transition, (ii) low loss
tangent, (iii) low activation energy, and (iv) low frequency dielectric dispersion. An anomaly in the ac conductivity was
found very close to phase transition temperature. The activation energy is found to decrease from 0.19 to 0.01 eV on increasing
Ba-concentration to 7% (x=0.07). Temperature field-dependent magnetization measurements of all the samples showed antiferromagnetic
transition at ∼15 K (for x=0.07). PBFN sample showed a slight increase in the coercivity (i.e., from 400 Oe (PFN) to 500 Oe
(PBFN, for x=0.07) at 2 K.
PACS 61.10.Nz; 68.37.Hk; 75.50.Ss; 75.60.Ej; 77.22.Ch; 77.22.Gm 相似文献
63.
One-pot three-component Kabachnik-Fields synthesis of α-aminophosphonates with high yields from the reaction between carbonyl compound, primary amine, and substituted phosphite can be carried out in a short period, using H-beta zeolite as a reusable catalyst. 相似文献
64.
Polycrystalline samples of Fe-modified PLZT (lead lanthanum zirconate titanate) are prepared by a mixed-oxide reaction technique.
The formation of the compound has been confirmed by X-ray powder diffraction studies. The unit cell structure of the material
has been found to be rhombohedral. Fourier-transform infrared reflection (FTIR) spectra have been recorded to correspond the
structural changes associated with the phase formation. The effects of Fe concentration on the microstructure and dielectric
constant of PLZT materials have been investigated. The ferroelectric phase transition of PLFZT materials is studied using
dielectric measurements, which shows a shift in the transition temperature towards the higher-temperature side with increased
Fe ion concentration. The piezoelectric constants of this system are investigated by the same way of changed contents of Fe
ion in the main PLZT compound. The optimum values of Qm, kp, and d33 are 73, 0.32 and 406. The electrical conductivity increases with the increase in Fe ion concentration.
PACS 77.80.Bh; 77.84.Dy; 77.22.Ch; 72.15.Eb; 06.60.Ei; 39.30.+w 相似文献
65.
Rishav Choudhary Julian J. Girard Sean Clees Sarah E. Johnson Jiankun Shao David F. Davidson Ronald K. Hanson Allen A. Aradi 《Proceedings of the Combustion Institute》2021,38(1):957-965
We report the first shock tube measurements of formaldehyde (CH2O) during the first stage ignition of n-heptane, 2-methylhexane and 3,3-dimethylpentane, in highly diluted fuel/oxygen mixtures in the pressure range of 7–10 atm and temperature range of 700–880 K. Combined time histories of all carbonyl (–C = O) species, CO and fuel were also measured simultaneously in an effort to study the impact of fuel structure on the concentration and the rate of evolution of first stage ignition products. Of the three isomers studied in this work, n-heptane was found to be the fastest, while 3,3-dimethylpentane was found to be the slowest. The differences in the time scale of formation, and plateau concentration of the intermediates between the isomers across the entire range of test conditions suggests a strong dependency of the measured time histories to fuel structure. These species therefore act as markers of the Negative Temperature Coefficient (NTC) behavior of fuels and can be used as targets for developing semi-empirical, hybrid chemistry models of complex, multi-component petroleum derived gasoline and jet fuels. The time histories reported in this work should prove very useful in the refinement of detailed kinetic models of n-heptane, and development of rate rules for branched alkane isomers. 相似文献
66.
Physics of the Solid State - The synthesis of the perovskites BiSmO3 was done by the solid-state reaction method. In this communication, the structural and detailed electrical (dielectric,... 相似文献
67.
The Langmuir monolayer at an air–water interface shows remarkably different surface pressure (π)–area (A) isotherm, when measured with the surface normal of a Wilhelmy plate parallel or perpendicular to the direction of compression of the monolayer. Such difference arises due to difference in stress exerted by the monolayer on the plate in different direction. In this article, we report the effect of changing the direction of substrate normal with respect to the compression of the monolayer during Langmuir–Blodgett (LB) film deposition on the morphology of the films. The morphology of the LB film of stearic acid is studied using an atomic force microscope. The morphology of the LB films is found to be different due to difference in the stress in different directions. The role of such surface morphology on the alignment of a nematic liquid crystal (LC) in LC cells is studied. The granular texture of LB films of stearic acid supports the homogeneous alignment of the LC whereas the uniform texture supports the homeotropic alignment of the LC. 相似文献
68.
69.
Adamson P Andreopoulos C Armstrong R Auty DJ Ayres DS Backhouse C Barr G Bishai M Blake A Bock GJ Boehnlein DJ Bogert D Cavanaugh S Cherdack D Childress S Choudhary BC Coelho JA Coleman SJ Corwin L Cronin-Hennessy D Danko IZ de Jong JK Devenish NE Diwan MV Dorman M Escobar CO Evans JJ Falk E Feldman GJ Frohne MV Gallagher HR Gomes RA Goodman MC Gouffon P Graf N Gran R Grant N Grzelak K Habig A Harris D Hartnell J Hatcher R Himmel A Holin A Huang X Hylen J Ilic J Irwin GM Isvan Z Jaffe DE 《Physical review letters》2011,106(18):181801
Measurements of neutrino oscillations using the disappearance of muon neutrinos from the Fermilab NuMI neutrino beam as observed by the two MINOS detectors are reported. New analysis methods have been applied to an enlarged data sample from an exposure of 7.25×10(20) protons on target. A fit to neutrino oscillations yields values of |Δm(2)|=(2.32(-0.08)(+0.12))×10(-3) eV(2) for the atmospheric mass splitting and sin(2)(2θ)>0.90 (90% C.L.) for the mixing angle. Pure neutrino decay and quantum decoherence hypotheses are excluded at 7 and 9 standard deviations, respectively. 相似文献
70.
Nanocrystalline samples of Pb1−yLay(Ti1−xMnx)(1−y/4)O3 (PLMT) (y=0.06, x=0, 0.04, 0.07 and 0.10) were prepared by mechanical activation process (i.e., ball milling) followed by some annealing. The formation of single phase tetragonal crystal structure is confirmed by high-resolution X-ray diffraction study and by High resolution transmission electron micrographs (HRTEM), nano-scale compounds. The electrical behavior (i.e., impedance (Z) and electrical modulus (M)) of PLMT ceramics was studied by impedance spectroscopy technique in high temperature range. This study was carried out by means of the simultaneous analysis of the complex impedance (Z?) and electrical modulus (M*) functions in a wide frequency range (1 kHz-1 MHz). Impedance analysis has shown the grain and grain boundary contributions by an equivalent circuit model. Modulus analysis has provided vast information on charge transport processes. The simultaneous representation of the imaginary part of impedance and electric modulus (Z″, M″) vs. frequency revealed the localization of relaxation. The activation energy obtained from relaxation data may be attributed to oxygen ion vacancies. 相似文献